Process for the preparation of water-dilutable coating binders based on acrylate copolymers, and their use

ABSTRACT

A process is disclosed for preparing water-dilutable, acrylate copolymer-based lacquer binders. A polycarboxylic component is reacted with an epoxide group-containing polyhydroxylic component, and the carboxylic groups are then at least partially neutralized. As epoxide group-containing monomers for the polyhydroxylic components, glycidyl(meth)acrylate and/or glycidylallylether are used in proportions from 0.1 to 3% by weight. Associated with cross-linking components and if required with other lacquer binders, these lacquer binders are suitable for producing water-dilutable baking enamels with a low auxiliary organic solvent content.

The invention relates to a process for the preparation ofwater-dilutable coating binders based on acrylate copolymers and totheir use for the formulation of water-thinnable baking enamels having alow content of organic auxiliary solvents.

Water-dilutable binders which are obtained by partial condensation of apolycarboxy component, which is soluble in water followingneutralization of the carboxyl groups, with a resin-like polyhydroxycomponent which is essentially not dilutable in water, and which aredistinguished by favourable viscosity characteristics on dilution withwater, are claimed in a series of protective documents, for example inAT Patent 328 587, AT Patent 379 607, AT Patent 388 738, AT Patent 388382 and EP 0 496 079 A2.

The preparation of acrylate copolymers in accordance with EP 0 496 079A2 requires a high level of concomitant analytical control measures inorder to ensure that the quality of these products remains constant.

It has now been found that it is possible, by reacting a polycarboxycomponent with a polyhydroxy component which contains epoxide groups, tocarry out the preparation of such water-dilutable acrylate copolymers ina more simple, more rapid and more reproducible manner.

The invention accordingly relates to a process for the preparation ofwater-dilutable coating binders based on acrylate copolymers, which areobtained by reacting a polycarboxy component with a polyhydroxycomponent followed by at least partial neutralization of the carboxylgroups, which is characterized in that

(A) from 15 to 40% by weight, based on solids content, of an acrylatecopolymer as polycarboxy component having an acid number of from 70 to240 mg of KOH/g, preferably from 100 to 200 mg of KOH/g, which has beenprepared in the form of a solution polymer from

(Aa) from 67 to 90% by weight of alkyl (meth)acrylates which contain analkyl radical of 1 to 12 carbon atoms, it being possible for theseesters to be replaced in a proportion of up to 50% by weight by aromaticvinyl compounds, preferably styrene, and

(Ab) from 10 to 33% by weight of α,β-ethylenically unsaturatedcarboxylic acids, preferably (meth)acrylic acid,

is mixed with

(B) from 60 to 85% by weight, based on solids content, of an acrylatecopolymer as polyhydroxy component having a hydroxyl number of from 90to 250 mg of KOH/g, preferably from 110 to 180 mg of KOH/g, and anepoxide equivalent of from 0.7 to 26.0 milliequivalents/100 g of solids,which has been prepared in the form of a solution polymer from

(Ba) from 40 to 79.9% by weight of alkyl (meth)acrylates which containan alkyl radical of 1 to 12 carbon atoms, it being possible for theseesters to be replaced in a proportion of up to 50% by weight of aromaticvinyl compounds, preferably styrene,

(Bb) from 20 to 59.9% by weight of monoesters of (meth)acrylic acid withdiols, which contain an alkylene radical of 2 to 4 carbon atoms or anoxyalkylene radical of 6 to 12 carbon atoms, and

(Bc) from 0.1 to 3% by weight of a monomer which contains epoxidegroups,

the data for the acid number and hydroxyl number always relating to thesolids content and the sums of the percentages for components (A) and(B) and, respectively, (Aa) and (Ab) and (Ba) to (Bc) necessarily giving100 in each case,

with the proviso that the mixture has an acid number of at least 15 mgof KOH/g, the solvent is removed in vacuo until the solids content ofthe batch is at least 95% by weight, the batch is diluted with anauxiliary solvent to a solids content of from 85 to 93% by weight, andthen the mixture is maintained at a temperature of from 100° to 150° C.,preferably from 110° to 130° C., until the epoxide equivalent of thebatch has fallen to less than 0.2 milliequivalent/100 g of solids.

The invention also relates to the use of the binders prepared by thisprocess, in combination with crosslinking components and optionally withother coating binders, for the formulation of water-thinnable bakingenamels having a low content of organic auxiliary solvents.

In comparison with the process described in EP 0 496 079 A2 it ispossible with the aid of the process according to the invention toprepare water-dilutable acrylate copolymers of similar composition witha simple procedure, a short duration of reaction and without risk ofgelation.

Components (A) and (B) are prepared in a known manner by solutionpolymerization, preferably in alcohols or glycol ethers. In thispolymerization the monomers are employed in the proportions indicated inthe main claim.

Monomers which are used as components (Aa) and/or (Ba) are (meth)acrylicesters of alkanols of 1 to 12 carbon atoms and also, if desired,proportions--that is, up to 50% by weight--of aromatic vinyl monomers,especially styrene.

Component (Ab) preferably comprises acrylic or methacrylic acid,although it is possible for other α,β-ethylenically unsaturatedcarboxylic acids such as maleic acid and its monoesters to be employedif desired.

As component (Bb) monoesters of (meth)acrylic acid with diols, whichcontain 2 to 4 carbon atoms, are employed, such as ethylene glycol,propylene glycol and butylene glycol and/or the corresponding isomericcompounds. In addition, it is also possible to use monoesters ofalkanediols of 6 to 12 carbon atoms which contain ether groups, forexample tri- or corresponding poly-ethylene glycol mono(meth)acrylatesand/or di- or corresponding poly-propylene glycol mono(meth)acrylates.

Monomers containing epoxide groups as component (Bc) are preferablyglycidyl (meth)acrylate and/or glycidyl allyl ether.

The polycarboxy component (A) has an acid number of from 70 to 240 mg ofKOH/g, preferably from 100 to 200 mg of KOH/g.

The hydroxyl number of the polyhydroxy component (B) is between 90 and250 mg of KOH/g, preferably between 110 and 180 mg of KOH/g, and theepoxide equivalent is from 0.7 to 26.0 milliequivalents/100 g of solids.

Components (A) and (B) are mixed in a proportion, based on solidscontent, of between 15:85 and 40:60, with the proviso that the mixturehas an acid number of at least 15 mg of KOH/g. Subsequently the solventsare substantially removed in vacuo and are replaced in part by auxiliarysolvents such as alcohols or glycol ethers, such that the solids contentof the mixture is from 85 to 93% by weight.

The reaction of the polycarboxy component (A) with the polyhydroxycomponent (B) which contains epoxide groups is carried out at from 100°to 150° C., preferably at from 110° to 130° C., until the epoxideequivalent of the batch has fallen to less than 0.2 milliequivalent/100g of solids. An appropriate neutralizing agent, such as ammonia and/oran alkylamine and/or an alkanolamine, is then added, and the batch isdiluted with water to the desired solids content.

The binders prepared in accordance with the invention are used, incombination with crosslinking components and optionally with othercoating binders, for the formulation of baking enamels having a very lowcontent of organic auxiliary solvents.

The binders are particularly suitable for the production ofwater-dilutable basecoats as are employed, for example, in theproduction-line finishing of cars for two-coat finishes consisting of acoloured and/or special-effect basecoat and a clearcoat.

Such water-dilutable basecoats additionally contain--optionally incombination with additional water-dilutable binders--crosslinkingcomponents, preferably amino resins and/or blocked polyisocyanates, andalso the additives, fillers and pigments which are familiar to theperson skilled in the art.

Suitable additional water-dilutable binders, which can also be used aspaste resins, are, in particular, polyester resins, polyacrylate resinsand polyurethane resins.

The water-dilutable basecoats are applied in a known manner incombination with clearcoats and are crosslinked at temperatures of up to160° C.

The examples which follow illustrate the invention without limiting itsscope. All parts and percentages are by weight unless stated otherwise.

1. Preparation of the Polycarboxy Components (A) and PolyhydroxyComponents (B) Used in the Examples

The copolymers were prepared in a known manner by solutionpolymerization in isopropanol, in accordance with a calculated solidscontent of 50% by weight for components (A) and 65% by weight forcomponents (B). The quantitative proportions and characteristics arecompiled in Table 1.

2. Examples 1 to 5

Preparation of the Acrylate Copolymers (AB1) to (AB5)

Components (A) and (B) are mixed in the proportions indicated in Table2. The isopropanol is removed in vacuo until the solids content of thebatch is at least 95% by weight. After dilution of the batch withdipropylene glycol monomethyl ether to a solids content of about 90% byweight, the mixture is maintained at a temperature of from 110° to 120°C. until the epoxide equivalent of the batch has fallen to less than 0.2milliequivalent/100 g of solids. After the end of the reaction the batchis cooled to 95° C., neutralized and diluted with deionized water.

The characteristics of the products according to Examples 1 to 5 arelikewise to be found in Table 2.

Analytical Determination of the Epoxide Equivalent

Milliequivalents of Epoxide Groups/100 g of Solids

About 0.2 g of the sample is weighed accurately on an analytical balanceand is dissolved with gentle heating in 25 ml of a mixture of 4 parts ofdichloromethane/1 part of glacial acetic acid. After the solution hasbeen cooled to room temperature 0.5 g of tetrabutylammonium iodide isadded. Following the addition of 3 drops of crystal violet (0.1% inglacial acetic acid) the mixture is titrated with 0.1N perchloric acidin glacial acetic acid, from blue-violet until the change-over point tograss green (green without a hint of blue|). In parallel with thesample, a control with no resin added must be determined. ##EQU1##A=Consumption in ml of 0.1N perchloric acid for sample B=Consumption inml of 0.1N perchloric acid for control

f=Factor for 0.1N perchloric acid

Determination of the Factor of 0.1N Perchloric Acid

About 200 mg of potassium hydrogen phthalate AR are weighed accuratelyon an analytical balance in a 300 ml conical flask, 30 ml of glacialacetic acid and 3 drops of crystal violet (0.1% in glacial acetic acid)are added, and the mixture is titrated with 0.1N perchloric acid inglacial acetic acid to the colour change-over point from violet to adefinite green. ##EQU2## W=Weight of potassium hydrogen phthalate AR inmilligrams C=Consumption in ml of 0.1N perchloric acid in glacial aceticacid

                  TABLE 1                                                         ______________________________________                                                        COMPONENT                                                                           (A1)   (A2)                                             ______________________________________                                        (Aa) Ethyl acrylate   --     25                                                    Butyl acrylate   --     35                                                    2-Ethylhexyl acrylate                                                                          30     --                                                    Methyl methacrylate                                                                            --     30                                                    Isobutyl methacrylate                                                                          27     --                                                    Styrene          18.5   --                                               (Ab) Acrylic acid     --     10                                                    Methacrylic acid 24.5   --                                                    Acid number mg of KOH/g                                                                        160    78                                               ______________________________________                                                        COMPONENT                                                                           (B1)   (B2) (B3) (B4) (B5)                              ______________________________________                                        (Ba) Ethyl acrylate   --     19   --   --   --                                     Butyl acrylate   --     14   --   30   23                                     2-Ethylhexyl acrylate                                                                          26     --   --   --   --                                     Methyl methacrylate                                                                            --     27   20   --   12                                     Isobutyl methacrylate                                                                          18     --   24   10   22.6                                   Styrene          24.2   --   --   31.8 10                                (Bb) 4-Hydroxybutyl acrylate                                                                        --     9    33   22   15                                     2-Hydroxyethyl methacrylate                                                                    31     30   21   --   17                                     Tripropylene glycol                                                                            --     --   --   6    --                                     methacrylate                                                             (Bc) Glycidyl acrylate                                                                              --     1    --   --   0.4                                    Glycidyl methacrylate                                                                          0.8    --   1    0.2  --                                     Glycidyl allyl ether                                                                           --     --   1    --   --                                     Hydroxyl number mg of                                                                          137    169  228  95   134                                    KOH/g                                                                         Epoxide equivalent                                                                             5.6    7.8  15.8 1.4  3.1                                    meq/100 g of solid resin                                                 ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        (all quantities relate to solids content)                                                  1       2       3     4     5                                    Example      (AB1)   (AB2)   (AB3) (AB4) (AB5)                                ______________________________________                                        Quantity/Component (A)                                                                     25      30      40    20    25                                                (A1)    (A1)    (A2)  (A2)  (A2)                                 Quantity/Component (B)                                                                     75      70      60    80    75                                                (B1)    (B2)    (B3)  (B4)  (B5)                                 Acid number mg of                                                                          40      48      31    16    20                                   KOH/g of the mixture                                                                       91.5    91.3    92.0  90.8  91.5                                 Solids content % by wt..sup.1)                                                Addition reaction                                                                          30/     15/     30/   60/   45/                                  min/°C.                                                                             120     115     115   120   120                                  Epoxide equivalent.sup.2)                                                                  0.12    0.18    0.08  0.12  0.09                                 meq/100 g of solid resin                                                      Neutralizing agent                                                                         DMA     TEA     DMA   DMA   DMA                                  Degree of neutralization                                                                   90      80      100   100   100                                  (% of the COOH groups)                                                        Dilution with H.sub.2 O to %                                                               42.3    43.5    41.8  43.2  44.6                                 by wt. solids content/                                                        supply form                                                                   pH of 10% strength                                                                         8.7     8.3     8.9   8.8   8.7                                  solution (20° C.)                                                      % by wt. of organic sol-                                                                   6.3     7.5     5.7   5.5   5.6                                  vent and amine in supply                                                      form                                                                          ______________________________________                                         .sup.1) % by weight solids content of the mixture after the addition of       dipropylene glycol monomethyl ether                                           .sup.2) after the end of the reaction                                         DMA = Dimethylethanolamine                                                    TEA = Triethylamine                                                      

3. Coating Performance Testing of the Acrylate Copolymers (AB1) to (AB5)3.1. Clearcoats in a Metallic Basecoat/Clearcoat System and WhiteCoating Materials

The formulations are compiled in Tables 3 and 4.

The indices 1) to 9) in Tables 3 and 4 denote:

1) Commercial melamine resin, of moderate reactivity, 85% strength inwater (Cymel® 373, Cyanamid)

2) Commercial silicone levelling agent for water-thinnable coatingmaterials (Additol® XW 329, Hoechst)

3) Commercial light stabilizer combination of benzotriazole UV absorber(Tinuvin® 1130, Ciba-Geigy) with sterically hindered amine (Tinuvin®292, Ciba-Geigy) in a ratio of 1:1

4) Commercial antifoam based on acetylenediols (Surfinol® E 104/50%, AirProducts)

5) Fully deionized water

6) HS value, as a measure of the content of volatile organic solvents:##EQU3## 7) Flow time according to DIN 53211/23° C. in seconds 8)Content of organic auxiliary solvents and amine in % by weight

9) Commercial titanium dioxide (Kronos® CL 310, Kronos)

The batches of coating material were adjusted to a pH of from 7.5 to 9.0with dimethylethanolamine and were diluted with deionized water to aviscosity corresponding to a flow time according to DIN 53211/23° C. ofabout 32 seconds.

The clearcoats were applied to coated steel panels (zincphosphatization, cathodic electrodeposition coating, filler, metallicbasecoat, using products which are employed in the automotive industry)by spraying at 23° C. and a relative atmospheric humidity of 60%. Aftera flash-off time of 10 minutes and a preliminary drying time of 10minutes at 80° C., the coatings were baked for 30 minutes at 140° C.

The white coating materials were applied to coated steel panels (zincphosphatization, cathodic electrodeposition coating, filler, usingproducts which are employed in the automotive industry) in an analogousmanner and baked.

The results are compiled in Tables 5 and 6, where indices (1) to (4)denote:

(1) measured with a Byk Type Colourgloss 2 gloss meter at an angle of60°

(2) an acetone-soaked cotton wool pad is placed on the coating film andthe time taken for the film to soften is measured

(3)

+: the coating film is unchanged after storage in water at 40° C. for240 hours

(+): the coating film has softened after storage in water at 40° C. for240 hours, but is regenerated after storage at room temperature forabout 2 hours

(4) with the coating applied in a wedge formation (max. 60 μm, min. 15μm), blistering and/or runs are noted in the baked coating film from thecoat thickness indicated.

                  TABLE 3                                                         ______________________________________                                        Acrylate copolymer (AB)/                                                                       Clearcoat                                                    supply form      1      2       3     4                                       ______________________________________                                        (AB1)            75.0                                                         (AB2)                   69.1                                                  (AB4)                           74.1                                          (AB5)                                 70.6                                    Melamine resin.sup.1)                                                                          16.0   15.3    9.4   12.4                                    Levelling agent.sup.2)                                                                         0.2    0.2     0.3   0.3                                     Light stabilizer.sup.3)                                                                        1.2    1.2     1.4   1.3                                     Antifoam.sup.4)  0.5    0.5     0.5   0.5                                     H.sub.2 O.sup.5) 7.1                                                                           13.8   14.3    14.9                                                           100    100     100   100                                     (AB): MF resin*.sup.)                                                                          70:30  70:30   80:20 75:25                                   Solids content in % by wt.                                                                     46.9   44.6    42    43.7                                    HS value.sup.6)  90.4   89.2    90.7  91.2                                    pH               8.7    8.7     8.7   8.6                                     Viscosity.sup.7) 30     30      30    30                                      Solvent + amine in the                                                                         5.0    5.4     4.3   4.3                                     coating material.sup.8)                                                       ______________________________________                                         *.sup.) based on solids                                                  

                  TABLE 4                                                         ______________________________________                                        Acrylate copolymer (AB)/                                                                         White coating material                                     supply form        1        2                                                 ______________________________________                                        (AB1)              46.3                                                       (AB3)                       51.0                                              Melamine resin.sup.1)                                                                            9.9      10.7                                              TiO.sub.2.sup.9)   24.8     23.3                                              Levelling agent.sup.2)                                                                           0.2      0.2                                               Antifoam.sup.4)    0.4      0.4                                               H.sub.2 O.sup.5)   18.4     14.4                                                                 100      100                                               (AB):MF resin*.sup.)                                                                             70:30    70:30                                             Solids content in % by wt.                                                                       53.2     54.1                                              HS value.sup.6)    94.5     94.6                                              pH                 8.5      8.4                                               Viscosity.sup.7)   32       35                                                Solvent + amine in the coating                                                                   3.1      3.1                                               material.sup.8)                                                               ______________________________________                                         *.sup.) based on solids                                                  

                  TABLE 5                                                         ______________________________________                                        Clearcoat       1      2       3     4                                        ______________________________________                                        Pendulum hardness                                                                             165    180     190   195                                      DIN 53157 in sec.                                                             Cross-hatch (DIN 53151)                                                                       0-1    0-1     0     0-1                                      Gloss (1)       89     86      86    84                                       Acetone resistance                                                                            2      3       2     2                                        in min. (2)                                                                   Water resistance (3)                                                                          (+)    (+)     +     +                                        Blistering tendency,                                                                          37     39      40    40                                       μm (4)                                                                     Tendency to run, μm (4)                                                                    42     40      40    38                                       ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        White coating material                                                                            1      2                                                  ______________________________________                                        Pendulum hardness   175    160                                                DIN 53157 in sec.                                                             Cross-hatch (DIN 53151)                                                                           1-2    2                                                  Gloss (1)           82     78                                                 Acetone resistance  2      2                                                  in min. (2)                                                                   Water resistance (3)                                                                              (+)    (+)                                                Blistering tendency,                                                                              41     37                                                 μm (4)                                                                     Tendency to run, μm (4)                                                                        40     42                                                 ______________________________________                                    

3.2. Lime Green Water-Dilutable Basecoat

3.2.1. Preparation of a Green Pigment Paste

20 parts of a chlorinated phthalocyanine pigment are predispersed usinga dissolver in a mixture of 20 parts of a paste resin according to EP0438090 A1 (paste resin 1), 35 parts of butoxyethanol and 0.5 parts ofdimethylethanolamine, and this mixture is then dispersed in a bead mill.The pigment paste is subsequently diluted with 24.5 parts of deionizedwater.

3.2.2. Preparation of a White Pigment Paste

60 parts of titanium dioxide are predispersed using a dissolver in amixture of 10 parts of a paste resin according to EP 0438090 A1 (pasteresin 1), 15 parts of butoxyethanol and 0.5 parts of dimethylethanolmineand this mixture is then dispersed in a bead mill. The pigment paste issubsequently diluted with 14.5 parts of deionized water.

3.2.3. Preparation and Application of the Lime Green Water-DilutableBasecoat

In a dissolver, 25 parts of the acrylate copolymer (AB3) are neutralizedwith 0.5 part of dimethylethanolamine. 8 parts of a 2:1 mixture ofbutylglycol and butyldiglycol, 2 parts of a commercially availableantifoam, 4 parts of an acidic acrylate thickener, 12 parts of a pasteresin according to EP 0438090 A1 (paste resin 1) and 5 parts ofcrosslinking agent (Cymel 323) are added. After homogenization of themixture, 10 parts of the green pigment paste obtained under 3.2.1. and 3parts of the white pigment paste obtained under 3.2.2. are added to themixture. Homogeneous mixing is again carried out, and the mixture isdiluted with 30.5 parts of deionized water.

The basecoat is applied to a phosphatized bodywork panel, which has beenprecoated with a cathodic deposition coat and with a filler, byspraying, in a dry-film thickness of 20 μm. This coating is then flashedoff at room temperature for 10 minutes, predried at 80° C. for 10minutes, and overcoated with a commercial, acrylate resin-basedautomotive production-line clearcoat, which cures by means of melamineresin, in a dry-film thickness of 35 μm. The two-coat topcoat is bakedat 130° C. (panel temperature) for 30 minutes.

The multi-coat paint system thus obtained meets, in terms of its opticaland mechanical properties, all of the requirements set by the automotiveindustry.

We claim:
 1. A process for the preparation of water-dilutable coatingbinders based on acrylate copolymers, which are obtained by reacting apolycarboxy component with a polyhydroxy component followed by at leastpartial neutralization of the carboxyl groups, wherein the processcomprises:mixing(A) from 15 to 40% by weight, based on solids content,of an acrylate copolymer as the polycarboxy component having an acidnumber of from 70 to 240 mg of KOH/g, which has been prepared in theform of a solution polymer from:(Aa) from 67 to 90% by weight of alkyl(meth)acrylates which contain an alkyl radical of 1 to 12 carbon atoms,it being possible for these esters to be replaced in a proportion of upto 50% by weight by aromatic vinyl compounds, and (Ab) from 10 to 33% byweight of α,β-ethylenically unsaturated carboxylic acids,with (B) from60 to 85% by weight, based on solids content, of an acrylate copolymeras the polyhydroxy component having a hydroxyl number of from 90 to 250mg of KOH/g, and an epoxide equivalent of from 0.7 to 26.0milliequivalents/100 g of solids, which has been prepared in the form ofa solution polymer from:(Ba) from 40 to 79.9% by weight of alkyl(meth)acrylates which contain an alkyl radical of 1 to 12 carbon atoms,it being possible for these esters to be replaced in a proportion of upto 50% by weight of aromatic vinyl compounds, (Bb) from 20 to 59.9% byweight of monoesters of (meth)acrylic acid with diols, which contain analkylene radical of 2 to 4 carbon atoms or an oxyalkylene radical of 6to 12 carbon atoms, and (Bc) from 0.1 to 3% by weight of a monomer whichcontains epoxide groups, wherein the data for the acid number andhydroxy number always relates to the solids content and the sums of thepercentages for components (A) and (B) and, respectively, (Aa) and (Ab)and (Ba) to (Bc) necessarily giving 100 in each case, with the provisothat the mixture has an acid number of at least 15 mg of KOH/g; removingthe solvent in vacuo until the solids content of the batch is at least95% by weight; diluting the batch with an auxiliary solvent to a solidscontent of from 85 to 93% by weight; and maintaining the mixture at atemperature of from 100° to 150° C., until the epoxide equivalent of thebatch has fallen to less than 0.2 milliequivalent/100 g of solids.
 2. Aprocess according to claim 1, wherein glycidyl (meth)acrylate and/orglycidyl allyl ether is employed as component (Bc).
 3. Water-dilutablecoating binders based on acrylate copolymers, produced according to theprocess of claim
 1. 4. Water-dilutable coating binders based on acrylatecopolymers, produced according to the process of claim
 2. 5. A processfor the preparation of water-thinnable baking enamels with a low contentof organic auxiliary solvents, comprising, combining the binders asclaimed in claim 3 with crosslinking components and optionally withother coating binders.
 6. A process for the preparation ofwater-thinnable baking enamels with a low content of organic auxiliarysolvents, comprising, combining the binders as claimed in claim 4 withcrosslinking components and optionally with other coating binders.
 7. Aprocess for the preparation of water-dilutable basecoats, comprising,combining the binders as claimed in claim 3 with crosslinkingcomponents, and further coating raw materials to produce water-dilutablebasecoats.
 8. A process for the preparation of water-dilutablebasecoats, comprising, combining the binders as claimed in claim 4 withcrosslinking components, and further coating raw materials to producewater-dilutable basecoats.
 9. A process for coating a substrate with atwo-coat paint system, comprising:applying a basecoat containing thebinders of claim 3 to the substrate; and applying a further clearcoat tothe substrate.
 10. A process for coating a substrate with a two-coatpaint system, comprising:applying a basecoat containing the binders asclaimed in claim 4 to the substrate; and applying a further clearcoat tothe substrate.
 11. A process for the preparation of water-dilutablebinders according to claim 1, wherein the acrylate copolymer (A) has anacid number from 100 to 200 mg of KOH/g.
 12. A process for thepreparation of water-dilutable binders according to claim 1, wherein theacrylate copolymer (B) has a hydroxyl number from 110 to 180 mg ofKOH/g.
 13. A process for the preparation of water-dilutable bindersaccording to claim 1, wherein the mixture is maintained at a temperatureof from 110° to 130° C., until the epoxide equivalent of the batch hasfallen to less than 0.2 milliequivalent/100 g of solids.
 14. A processfor the preparation of water-dilutable binders according to claim 1,wherein the aromatic vinyl compounds of (Aa) comprise styrene.
 15. Aprocess for the preparation of water-dilutable binders according toclaim 1, wherein the α,β-ethylenically unsaturated carboxylic acids of(Ab) comprise (meth)acrylic acid.
 16. A process for the preparation ofwater-dilutable binders according to claim 1, wherein the aromatic vinylcompounds of (Ba) comprise styrene.